Metal treating process



United States Patent US. Cl. 1061 9 Claims ABSTRACT OF THE DISCLOSURE A process for the currentless production of a copper coating on ferrous metal surfaces by treating the ferrous surfaces with an aqueous acidic solution containing copper ions, chloride ions, and an organic modifying agent, the organic modifying agent being an acridine compound. The preferred acridine compound is 3,6-bis-(dimethylamino)-acridine.

This invention relates to a process for the treatment of ferrous metal surfaces and more particularly relates to an improved process for the currentless copperplating of ferrous surfaces.

Heretofore, it has been known that the cold Working of ferrous metals can be facilitated by first applying a copper coating to the workpiece to be worked. It is also known that suitable copper coatings for this use can be produced without the use of current by contacting the ferrous surfaces with an aqueous acidic solution containing copper ions and chloride ions. In such processes, however, it has often been difficult to consistently obtain a good, strongly adherent coating, so that numerous proposals have been made for the addition of various and diverse organic compounds as modifying agents in such coating solutions.

For example, in German Pat. 714,437, it has been proposed to add to the copper coating solutions strong organic inhibitors which greatly delay the dissolution of iron, even in hydrochloric acid. Typical of the types of organic materials disclosed are coal tar bases, the bases extracted from animal distillates, aldehyde amine reaction products, aldehyde ketone reaction products, various amino acids, alkaloids, such as quinine and quinoidine and their sulfurized derivatives. Exemplary of specific compounds disclosed in this patent for this use are dimethylnaphthoquinoldine, anhydroformaldehyde aniline, tetramethyldiaminodiphenylmethane, acetaldehyde o toluidine condensation products, their salts and the like. Additionally, this patent has indicated that weak inhibitors, such as o-toluidine and aniline, are not suitable.

In US. Pat. 2,410,844, polyhydroxythiols are proposed as additives for currentless copperplating solutions and in British Pat. 927,576, ethoxylated long-chain aliphatic amines are disclosed as being particularly advantageous modifying agents.

Additionally, in French Pat. 1,257,758, various organic compounds are disclosed as being suitable as brighteners and grain-improving agents for such coating baths. These include condensation products of fatty alcohols, fatty 3,535,129 Patented Oct. 20, 1970 ice acids, tall oil, alkylphenols, fatty amines, substituted thioureas with ethylene oxide, long-chain organic amines, sugars having a reducing action, decomposition products of sugar, salts of quaternary ammonium bases, such as laurylpyridinium sulfate, aryl sulfides and sulfoxides.

In spite of this wide variety of known organic modifying agents, difiiculties in obtaining uniform adherent copper coatings have repeatedly been encountered in commercial practice. Although it has been found that at elevated operating temperatures, e.g., 6 0 to degrees Centigrade, more uniform results may be obtained, when operating at or near room temperature, it has not been possible consistently to produce a bright, strongly adherent, even copper coating on steel wire rods, brightannealed or black-annealed predrawn steel wire.

It is, therefore, an object of the present invention to provide an improved process for the currentless production of a copper coating on ferrous metal surfaces.

A further object of the present invention is to provide an improved currentless copper coating process for ferrous metal, which process can be satisfactorily operated at substantially room temperature.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a process for the currentless production of a copper coating on ferrous metal surfaces, which process comprises contacting the ferrous metal surface to be treated with an aqueous, acidic solution containing copper ions, chloride ions, and an organic modifying agent, which organic modifying agent is an acridine compound, and forming a copper coating on the ferrous surfaces thus-contacted.

The use of acridine compounds as organic modifying agents in a currentless copperplating bath results in the consistent production of a more uniform, adherent coating on the ferrous surfaces treated. The results obtained with these compounds are somewhat surprising in that these compounds are, generally, of the type belonging to the group of coal tar bases which have heretofore been known as inhibitors. The use of other compounds of this general class, however, for example, pyridine, pyrrolidine, N-methyl 2 pyrrolidine, imidazole, pyrazole, pyrazine, pyrimidine, quinoline, isoquinoline, 8-hydroxyquinoline, benzoquinoline, naphthoquinoline, quinoxaline or aniline, result in poorly adherent copper coatings which vary in appearance from bright to dark. In view of these results, it was, therefore, unexpected that the acridine compounds should consistently produce bright, strongly adherent, even copper coatings, even when used at substantially room temperature.

More specifically, in the practice of the present invention, ferrous metal surfaces to be coated are contacted with an aqueous acidic copper plating bath containing copper ions and chloride ions, to which has been added an acridine compound. By acridine compounds, it is intended to refer to both acridine itself as well as its derivatives, such as 3,6 bis (dimethylamino)-acridine, acriflavine, chrysaninline, and the like. Of these particularly good results have been obtained when using 3,6-bis-(dimethylamino)-acridine, which material is commonly referred to as acridine orange. It is to be appreciated that the above are merely exemplary of the acridine type compounds which may be used and that other similar acridine derivatives, which function in the same manner, are also suitable.

The coating baths, in which the above acridine type modifiers are incorporated, are conventional aqueous, acidic copperplating baths, as are known to those in the art. Such baths contain copper ions, typically in amounts of within the range of about 0.1 to 1.0 percent by weight, chloride ions, typically in amounts within the range of about 1.0 to 3.0 percent by weight, and are typically at a pH Within the range of about to 2. These coating baths may also contain sulfate ions, and the solution is, desirably, an aqueous solution of sulfuric acid. Additionally, as the coating bath is used, ferrous ion will also be built up in the bath. Desirably, these coating baths will contain the acridine modifying compound in amounts within the range of about 0.01 to 1.0 gram per liter. Although amounts which are outside of this typical range may also A be used, particularly the amounts in excess of 1.0 gram per liter, it has been generally found that such larger amounts do not generally have any material additional advantageous effect on the bath.

The copper coating baths of the present invention may be built up using any suitable acid soluble components containing the desired ions, as have been indicated above. Typically, the copper is incorporated in the bath as a copper sulfate, the chloride ions as the alkali metal chlorides, and particularly sodium chloride, the sulfate ions as the alkali metal sulfates, while the acridine compounds may be used in their basic form or as salts. If desired, the acridine compounds may be admixed with the salt mixtures which are used for preparing and replenishing the copperplating baths, these mixtures containing, for example, copper sulfate and sodium chloride. Alternatively, however, the acridine compounds may be added separately, as for example, by making them up as a solution in an alcohol, such as ethanol. It has been found that the amounts of the acridine compound which are necessary for replenishing the bath are relatively small. In general, the consumption of the acridine compounds in the bath is within the range of about 0.01 to 0.1 gram per square meter of the copperplated ferrous metal surface produced.

A particularly suitable copper coating bath for use in the method of the present invention is one containing the following components in the amounts indicated.

Components: Amount Copper ions percent by weight 0.4 to 0.7 Chloride ions do 1.5 to 2.5 Acridine orange grams per liter 0.06 to 0.1 pH 0.5

Desirably, this bath has a ratio of about 2.0 percent sodium chloride per 0.008 percent acridine orange.

The copperplating baths of the present invention may be applied to the ferrous metal surfaces to be treated using any convenient technique, although dipping or immersion techniques are preferred. Desirably, the baths are used at temperatures which are at or close to room temperature, i.e., 20 degrees centigrade, and are typically used at temperatures which are not substantially in excess of about 40 degrees centigrade. While it is possible to utilize higher bath temperatures, e.g., 60 to 70 degrees centigrade or even higher, such higher temperatures, generally, do not result in any further technical advantage and do cause undesirable heating costs in the process.

Desirably, the ferrous metal workpieces are cleaned prior to being contacted with the copperplating solutions, suitable cleaning techniques including annealing, degreasing, and/or pickling. Typically, the cleaned ferrous surfaces are contacted with the copper coating bath for a period of from about 1 to 15 minutes and copper coatings having a weight of about 5 grams per square meter are thus formed. Obviously, other treating times may also be used, which are either greater than or less than the typical times set forth, thereby varying the thickness of the copper coating which is produced.

As has been previously noted, as the coating bath is used, iron will accumulate and build up in the bath. It has been found, however, that the beneficial effect of the acridine compounds is not diminished even where the ferrous iron has built up to as high as 30 to 40 grams per liter. This is yet another advantage of the present invention, over those of the prior art.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. In these examples, unless otherwise indicated, parts and percents are by weight and temperatures are in degrees centigrade. It is to be appreciated, however, that these examples are merely exemplary of the present invention and are not to be taken as a limitation thereof.

EXAMPLE 1 In a wire drawing plant, various qualities of steel wire rod and bright-annealed and black-annealed wire of steel were freed from oxide coatings by immersion in a percent by weight aqueous solution of sulfuric acid at 60 degrees centigrade. The workpieces were then rinsed in cold water and immersed for two minutes at room temperature, degrees centigrade, in an aqueous copperplating solution containing 13 grams per liter copper sulfate, 32 grams per liter sodium chloride, 17 grams per liter of sodium sulfate, 1 gram per liter of ferrous sulfate, 50 grams per liter of sulfuric acid and 0.08 gram per liter of acridine. This solution was agitated by introducing air into it. After immersion in the solution, the workpieces were rinsed in water and dried. All of the wires thustreated were found to have a bright, uniform copper coating which had very good adhesion. After the wires had been cold-drawn, with a total reduction in cross section of from 70 to 90 percent, using conventional dry and wet drawing lubricants, a cohesive copper coating was still visible on the surface of the wire.

EXAMPLE 2 The procedure of Example 1 was repeated with the exception that the acridine in the copper coating bath was replaced with 0.06 gram per liter of acridine orange. The results obtained corresponded substantially to those obtained in Example 1.

EXAMPLE 3 To demonstrate the beneficial effect of acridine compounds, a series of comparison tests were carried out with a base solution which contained 15.6 grams per liter of copper sulfate, 22.8 grams per liter of sodium chloride and millimeters per liter of 96 percent sulfuric acid. Ferrous ions, in the form of ferrous sulfate were then added to the baths in amounts of 0.4 gram per liter and grams per liter, respectively. Various modifying agents, as indicated hereinafter, were also added to the base solution in an amount of 80 milligrams per liter.

Steel wire rods, predrawn bright-annealed steel wire and predrawn black-annealed steel wire were then pickled by immersion for 15 minutes in a 20 percent by weight aqueous sulfuric acid solution at degrees centigrade. The wire was then rinsed with water, dipped for 15 minutes at room temperature in a motionless copper-plating bath, as described above, and after removal from the copper-plating bath, the wires were rinsed with water and dried. The surfaces of the 'wires were then evaluated as to appearance and rated as 1 for bright and good; 2 for medium; and 3 for dark. The strength of adherence of the copper coating on the wire was then tested by winding the wires around a mandrel having a diameter of 2 centimeters. The coatings were then rated as 1 for no cracking off of the coating; 2 for cracking off of the coating in places; and 3 for cracking 011 of the coating over large areas. Using this procedure, the results obtained were as follows:

TABLE I Wire rods Predrawn, bright annealed steel wire Predrawn, black-annealed steel wire 0.4 g./l. Fe II 40 g./l. Fe II 0.4 g./1.,Fe II 40 g./l. Fe II 0.4 g./l. Fe II 40 g,/l. Fe II Strength Strength Strength Strength Strength Strength Modifym agent Appearof adher- Appearof adher- Appearof adher- Appeal'- of adher- Appearof adher- Appearof adher- (80 rng./l. ance ence ance ence ance ence anee ence ance euce ance enee Aeridine 1 l 1 1 1 1 1 1 1 1 1 1 Aeridine orange 1 1 1 1 1 1 1 1 1 1 1 l Acriflaviue 1 1 1 1 1 2 1 2 1 2 1 2 Chrysaniline- 1 1 1 1 1 2 1 2 1 2 1 2 Pyridine 3 3 3 3 3 3 3 3 3 3 3 3 Quinoline- 2 3 3 3 2 3 3 3 2 3 3 3 Isoquinoline- 2 3 3 3 2 3 3 3 2 3 3 3 Alquad 1850 3 3 3 3 3 3 3 3 2 3 3 3 Geuepol S 150 3 3 3 3 3 2 3 3 2 3 3 3 Merpoxen OLF 8O 3 3 3 3 3 3 3 3 3 3 3 3 3 Merpoxen NO 230 4 1 2 1 2 l 3 1 3 1 3 1 3 Merpoxen TA 3 3 3 3 3 3 3 3 3 3 3 3 Ethemeen l8-60 1 1 2 2 1 2 2 3 l 3 2 3 The following information is given by the suppliers:

2 Genepol S 150: hydroxyethylated stearyl alcohol with mols. 3 Merpoxen OLF 80: hydroxyethylated oleic acid with 8 mols.

While therehave been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention, as it is realized that changes therewith are possible and it is intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A process for the currentless production of a copper coating on a ferrous metal surface which comprises contacting the ferrous metal surface to be treated with an aqueous acidic solution consisting essentially of copper ions in an amount of from about 0.1 to about 1.0 percent by weight, chloride ions in an amount of from about 1.0 to about 3.0 percent by weight and an acridine compound in an amount of from about 0.1 to about 1.0 gram per liter, and maintaining the aqueous solution in contact with the ferrous surface for a period sufficient to efiect the formation of the desired copper coating.

2. The process as claimed in claim 1 wherein the aqueous acidic solution has a pH within the range of about 0 to 2 and contains the copper ions in an amount within the range of about 0.4 to 0.7 percent by weight and the chloride ions in an amount within the range of about 1.5 to 2.5 percent by Weight.

3. The process as claimed in claim 2 wherein the acridine compound is acridine.

4 Merpoxen NO 230: C Hw-(C@Hi)O[CHzCH O]zaH. 5 Merpoxen TA: hydroxyethylated tall oil. 6 Ethemeen 18/60: hydroxyethylated stearyl amine.

6. The process as claimed in claim 4 wherein the aqueous acidic solution is at a temperature which is not substantially in excess of about 40 degrees Centigrade.

7. The process as claimed in claim 5 wherein the ferrous surface is immersed in the aqueous acidic solution for a period of from about 1 to 15 minutes.

8. The process as claimed in claim 6 wherein the ferrous surface is immersed in the aqueous acidic solution for a period of from about 1 to 15 minutes.

9. A composition for the currentless copper plating of ferrous metal which comprises an aqueous acidic solution consisting essentially of copper ions an amount of from about 0.1 to about 1.0 percent by Weight, chloride ions in an amount of from about 1.0 to about 3.0 percent by weight and an acridine compound in an amount of from about 0.01 to about 1.0 gram per liter.

References Cited UNITED STATES PATENTS 3,135,632 6/1964 Lucas et al. 25279.4 3,141,780 7/1964 Simon et a1. 106--1 3,246,995 4/1966 Moore 1061 DONALD J. ARNOLD, Primary Examiner L. B. HAYES, Assistant Examiner US. 01. X.R. 117 130, 

